The present invention relates to a latch device for a vehicle door with a motorized closure assembly, and particularly relates to a compact latch device suitably used in a vehicle back door.
U.S. Pat. No. 5,520,425 conventionally proposes a latch device for a vehicle door which comprises a latch assembly holding a vehicle door in a closed state by engaging with a striker fixed to a vehicle body, and a motorized closure assembly displacing the latch assembly into a full-latched state from a half-latched state so as to close the door completely.
The above prior art motorized closure assembly is designed so as to be arranged in a place separated from the latch assembly, so that it is unsuitable for use in a back door which has a narrow attaching space.
U.S. Pat. No. 4,986,579 describes a latch device of a vehicle door having an outer panel and an inner panel. This prior art latch device has a latch assembly (A) which is fixed to an end portion of the door and has a latch (7) engageable with a striker (81) fixed to a vehicle body and a ratchet (15) for holding the engagement between the latch (7) and the striker (81) by engaging with the latch (7); said latch (7) being rotated against a resilient force of a spring (9) from a door-opening position to a full-latched position through a half-latched position by engaging with the striker (81); said latch (7) being supported by a latch shaft (8); said ratchet (15) being supported by a ratchet shaft (16) parallel to the latch shaft (8); a motorized closure assembly (40) which is attached to the door in proximity to the latch assembly (A) and has an electric motor (43), an output member (57) rotated by the electric motor (43), a rotating lever (58) for rotating the latch (7) from the half-latched position to the full-latched position when rotated, and a connecting member (59) displaceable between a connecting position where rotation of the output member (57) can be transmitted to the rotating lever (58) and disconnecting position where the rotation of the output member (57) cannot be transmitted to the rotating lever (58); a switch (49) for detecting the half-latched position of the latch (7) so as to operate the motor (43); a spring (65) for biasing the connecting member (59) toward the connecting position; a fail-safe lever (60) displacing the connecting member (59) into the disconnecting position against the resilient force of the spring (65) when rotated; said latch (7) having a latch arm (20) which extends toward the inner panel and is overlapped with a rotating locus of the rotating lever (58) when the latch (7) is located in the half-latched position; and said ratchet (15) having a ratchet arm (24) which extends toward the inner panel.
The latter latch device has a disadvantage in that the latch arm (20) and the ratchet arm (24) extend toward the inner panel of the door. In the latch assembly, interior and exterior sides of the latch assembly are defined by the position of an opening portion into which the striker enters when the door is closed, which opening portion must be formed on the interior side of the latch assembly at any time. Further, the distances between the opening portion and the latch shaft or the ratchet shaft should be reduced as much as possible to compactly form the latch assembly. Therefore, it is impossible to increase lengths of the latch arm (20) and the ratchet arm (24) which extend toward the inner panel of the door, thereby large rotating torque is required to rotate the latch (7) toward the full-latched position from the half-latched position by a contact of the rotating lever (58) and the latch arm (20), and the motorized closure assembly (40) is large-sized. Similarly, large force is also required when the ratchet arm (24) is rotated.
Further, the latch device in the latter well-known example also has another disadvantage in that the motor (43) is greatly projected to the interior side of the latch assembly.